/*
day430 
2020.10.31 
*/
#include<iostream>
#include<vector>
#include<cstring>
using namespace std;


 
class Solution {
public:
    string makeGood(string s) {
		vector<char> vec;
		for(int i=0;i<s.size();++i)
		{
			if(vec.empty())
			{
				vec.push_back(s[i]);
			}
			
			else if( abs(vec.back()-s[i]) ==32 )
			{
				vec.pop_back();
			}
			else
			{
				vec.push_back(s[i]);
			}
		}
		
		string res(vec.begin(),vec.end());
		
		return res;
    }
    
	
};

int main()
{
	return 0;
}
